“Joint replacement in a severely obese patient is a
physically challenging and demanding task for the surgeon and also poses
increased risk to the patient,” said Dr. Huffaker. “Multiple studies have
demonstrated increased operating time, increased complication rates, and
decreased functional outcomes in patients with increasing BMI. This has led
many surgeons to place BMI restrictions on joint replacement candidates.
Because obesity is commonly considered to be reversible, this appears at face
value to be a reasonable option. However, we were interested in what this means
for the patient. When a morbidly obese patient is told to lose weight, how
reasonable is this request? What is the likelihood of success? How much time
will this take?”

Many patients fall
shortThe researchers conducted a retrospective review of 710 patients who
participated in a nonsurgical weight-reduction program at a single hospital
between 2010 and 2014. All participants were actively enrolled in the program
for at least 1 year, were at least 50 years old, had a starting body mass index
(BMI) greater than 30 kg/m2, and did not undergo bariatric or joint replacement
surgery. Overall, 133 had hip or knee OA and 576 did not. Of those, 44 patients
with OA and 172 without OA were morbidly obese (BMI ≥ 40 kg/m2). The
researchers determined group differences in BMI of 5 percent to be clinically
significant and powered the study accordingly.

Dr. Huffaker and his colleagues found that 17 percent of
morbidly obese patients with OA and 18.2 percent of morbidly obese patients
without OA lost enough weight to decrease their BMI below the morbidly obese
(40 kg/m2) threshold. They noted that 95 percent of patients who achieved such
weight loss started with a BMI of less than 44 kg/m2. The mean time to realize
the goal was 145 ± 37 days following program enrollment. The amount of time it
took patients to lose 5 percent of their body weight was not significantly
different across cohorts.

“Only about 1 in 5 morbidly obese patients were able to
successfully lower their BMI below 40 kg/m2 within 1 year of enrollment in the
weight-loss program,” said Dr. Huffaker. “Not surprisingly, the more obese the
patient was, the less likely he or she was to get below the threshold. Based on
our data, for 83 percent of morbidly obese patients with OA involved in
nonsurgical weight management alone, a 40 kg/m2 cutoff represented an
insurmountable barrier for joint replacement surgery. And patients who started
with a BMI over 45 kg/m2 had a less than 10 percent chance of losing enough
weight to get below the 40 kg/m2 threshold. Most of those who were successful
were able to do so within 3 to 6 months. Morbid obesity appears to have only
limited reversibility for a great majority of patients.”

Unreasonable
expectationsDr. Huffaker stated that, although BMI cutoffs may represent a simple
approach to filtering patients, they can create an unreasonable expectation of
weight loss on many patients and can limit access to an important and
life-altering procedure.

“Based on our findings, it is reasonable to place
morbidly obese patients on a 4- to 6-month trial weight-loss regimen. A small
number will be successful,” he said. “Although patients with starting BMI over
45 kg/m2 are less than 10 percent likely to lose weight below 40 kg/m2, 1 in 3
patients may be expected to lose at least 5 percent of their body weight during
this time.

“Following this period, we recommend a candid
conversation with the patient regarding the significant risks of joint
replacement in the morbidly obese, including discussion of more aggressive
surgical weight loss options versus an increased risk of perioperative
complications given their current weight,” said Dr. Huffaker. “We do not advocate
ignoring the effects of obesity on surgical outcomes and risks, but offer these
data as a caution against blanket weight restrictions, as this may be a
potentially discriminatory practice. We suggest instead that weight be
considered an optimizable chronic illness, much as chronic obstructive
pulmonary disease, diabetes, hypertension, etc.”

Dr. Huffaker’s
coauthor is Nicholas J. Giori, MD.

Details of the
authors’ disclosure as submitted to the Orthopaedic Disclosure Program can be
found in the Final Program; the most current disclosure information may be
accessed electronically at www.aaos.org/disclosure